When I hear "riding up" I know that most divers will recommend a crotch strap. I do consider a crotch strap to be an important component of a rig. However, the reason their BC, whatever it is, is riding up, especially if they have a weight belt instead of weight integration is being too nearly vertical in the water and being over weighted such that the air goes to the shoulder or top area and the weight being more centrally located amidships (hips) results in a vertical "walking" position in the water**. And of course the BC then rides up. A crotch strap would certainly prevent the riding up and the strap would be under tension as that does not correct the underlying weight and trim problem.
My two warmer water rigs, left VDH plate with VDH 22# wing, right Oxy 18 Mach V with Oxy soft plate. I much prefer the Oxy soft plate and only use the metal VDH plate for solo nowadays. This because it has better ability to mount/clip an auxiliary bottle and distribute the load. If I forget to attach the crotch strap I usually do not notice, it is not a big deal. It never has a load on it so it is just a one inch soft Nylon.
A VDH plate rigged and a VDH 18# wing mounted on an unrigged Oxy Travel soft plate.
The Oxy Travel soft plate is very comfortable in a rash guard and I dived that way in the Red Sea and the water being near 87 degrees in Cozumel the same a few days ago. My temperate water rig is an Oxy 30# Mach V on a stainless Freedom Plate. In any case, I never notice any tension in my crotch strap, it is hanging loose because my weight, trim are correct and I am horizontal in the water most times unless I do not want to be. Soft plates are intended for use with aluminum tanks or at least cylinders which are not significantly negative. The negative HP steel tanks will tend to flop side to side. I have used them with soft plates successfully but the metal plate is more stable.
** Uh, I do come across divers who have the opposite issue, their rear ends and legs go up and they are always drifting to the surface (my wife
, a dive buddy just a few days ago). If you have a pear shape this could be a problem. It is still a weight and trim issue. For some near 40 years my wife would occasionally revert to this annoying habit. That is until she got her VDH wing and for whatever reason for the four years she has used it not once did she float off like a helium balloon resulting in my having to chase after her
. Beats me.